Brian Reynolds, the chief game designer at social and mobile game giant Zynga, is leaving the company.

Joystiq reports (and Gamasutra can independently confirm) that the former lead designer of Firaxis' classic Civilization II is leaving to "pursue other opportunities," according to an internal statement issued by Zynga.

Reynolds' departure is the latest in the Zynga brain drain that has seen the departures of much of its executive and creative staff over the past several months.

Reynolds was hired away from Big Huge Games in 2009 to become the chief designer of Zynga's Baltimore studio and, later, the entire company.

In addition to Civilization II, Reynolds was also the lead designer of Alpha Centauri, Colonization, Rise of Nations, Rise of Legends and, at Zynga, led the development of Frontierville.